Modeling Agroecosystem Services under Simulated Climate and Land-Use Changes

Ecological functioning of the intensive, homogeneous agroecosystems in the Chippewa River Watershed (CRW), MN, USA, can be improved by reducing soil erosion, runoff, and nutrient leaching. These ecosystem services can be achieved through increased perennials in crop rotations to diversify land use and sustain carbon sequestration. We calibrated, validated, and used APSIM software to simulate the effect of 100 yrs each of historical and future climate change scenario (IPCC-A2) on biophysical processes in representative soil types of the predominant farming systems in CRW. The interrelationships between crop rotations, soil types, climate variables, and ecosystem services indicated that not all objectives of sustainable agro-ecosystem are compatible, and tradeoffs among them are necessary. Site-specific and diversified crop rotations that comply with the environmental constraints of climate and soils could lead to more efficient implementation of strategies to improve ecosystem services in the watershed if current management practices of high external inputs and tillage persisted. 1. Introduction The extent and global scale of the environmental costs associated with intensive agriculture are already documented [1], and their effects on ecosystem services have been extensively researched [2, 3]. Ecological functioning of the intensive agroecosystems in the Upper Midwest, in general [4], and in MN’s Chippewa River Watershed (CRW), in particular, is being compromised by soil erosion, runoff, and nutrient leaching [5, 6]. The land use in CRW is predominately centered on commodity production systems that deliver corn, soybean, and livestock products for domestic consumption and for an expanding export market [6, 7]. Similar to other conventional land-use systems in the Upper Midwest of the Corn Belt (i.e., corn-soybean rotation, conventional tillage, N fertilizer), losses of ~30% of the average 125？kg applied nitrogen (N) per ha to subsurface drainage in CRW are not uncommon [7, 8]. The rise in intensive, homogeneous croplands, especially corn production systems, is responsible for a substantial proportion of the increase in NO3-N values observed in surface and underground waters of the Midwest since the 1970s. River-born nutrients, especially NO3-N from tile-drained fields in the CRW, contribute to environmental pollution within and beyond the watershed [9]. Increased corn production as a feedstock for ethanol would result in a concomitant increase in N loads of ~5 to 18% [10]. This raises concerns about the environmental, agronomic, and economic